Integer to Roman

Problem Statement

Given an integer, convert it to a roman numeral.
Input is guaranteed to be within the range from 1 to 3999.

Programming Language: C#
Run Time Complexity: O(N)
Space Complexity: Constant space
Resources: http://en.wikipedia.org/wiki/Roman_numerals
Source: https://leetcode.com/problems/integer-to-roman/

Solution

public string IntToRoman(int num)
{
    // Maintain a mapping of numbers to roman numerals staring from highest numeral
    int[] integer = { 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 };
    String[] roman = { "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I" };
    
    // Output 
    string output = "";

    // Input validation (Num should be in the range of 1-3999)
    if (num <= 0)
        return output;

    for (int index = 0; index < integer.Length; index++)
    {
        int result = num / integer[index];

        // Append the roman numeral equal to the result 
        while (result > 0)
        {
            output += roman[index];
            result--;
        }

        // Continue the processing with the remainder
        num = num % integer[index];
    }

    // return output
    return output;
}